Field of the Invention
The present invention relates to an image transfer sheet comprising a support, a transfer layer provided on one side of the support and a backing layer provided on the other side of the support, and an image transfer method using such an image transfer sheet. An image can be formed on the transfer layer of the image transfer sheet using a variety of image forming apparatus, and the thus formed image-bearing transfer layer can be transferred to other image-receiving members such as cloth, canvas, plastic goods, paper, wood, leather, glass, earthenware and metal.
In the present invention, the image can be formed on the image transfer sheet, for example, using the following image forming apparatus:
1) an electrophotographic copying apparatus capable of producing a toner image by the xerography comprising an electrostatic image transfer step, PA1 2) a printer capable of transferring a thermofusible ink image or sublimation-type dye image by the thermal image transfer recording method, and PA1 3) an ink-jet printer capable of producing an aqueous ink image or a thermofusible ink image by the ink-jet process. PA1 (1) A toner image is transferred to the image transfer sheet and fixed thereon under the application of heat and/or pressure thereto by the electrophotographic process. PA1 (2) An image is transferred imagewise from a thermofusible ink layer or a sublimable-dye-containing layer of a thermal image transfer recording medium to the image transfer sheet. PA1 (3) An image comprising an aqueous ink or a thermofusible ink is formed on the image transfer sheet by ink-jet process.
Discussion of Background
In recent years, with the spread and development of the copying and printing apparatus, not only the originally-developed use of each apparatus, that is, to produce an image to a sheet of plain paper, but also new uses have been actively studied based on the applied functions of the apparatus.
For example, there is proposed a method of transferring an image formed on an image transfer sheet using the copying and printing apparatus to an image-receiving member such as cloth, leather, canvas, plastics, wood, glass, earthenware or metal, and fixing the image thereto. To be more specific, the above-mentioned image transfer method can be effectively applied to the manufacturing of clothes such as T-shirts, sweat shirts, aprons and jackets, cups, trays, stained glass, panels, and reproduced pictures which are made to order, or designed to be sold on a small scale, not by mass-production. Further, such demand has greatly expanded because high quality images can be more easily printed on the image-receiving members by using a full-color electrophotographic copying apparatus.
There is conventionally known an image transfer sheet for use with the image transfer method comprising the steps of forming a copied or printed image comprising a toner, thermofusible ink, sublimable dye or aqueous ink thereon and transferring the thus formed image to an image-receiving member, for instance, as disclosed in Japanese Laid-Open Patent Application 52-82509. According to this application, the image transfer sheet comprises a support, an adhesive layer formed thereon comprising an adhesive material selected from the group consisting of a silicone compound and a fluorine-containing polymer, and an undercoat layer (which is referred to as a transfer layer in the present invention) which is formed on the adhesive layer and comprises a specific low-temperature fusible polymer. As the low-temperature fusible polymer, there are disclosed vinyl chloride, vinyl acetate, methyl methacrylate, ethyl methacrylate, butyl methacrylate and vinylidene chloride; and mixtures, compounds and copolymers thereof. At the image transfer step, the image-bearing undercoat layer of the image transfer sheet is softened and completely transferred to an image-receiving member.
The above-mentioned conventional image transfer sheet can be stably stored at room temperature. However, when the ambient temperature increases to 50.degree. C., the low-temperature fusible material for use in the undercoat layer is softened and the softened undercoat layer unfavorably tends to adhere to the support side of another image transfer sheet while the image transfer sheets are piled up during the storage. This causes a so-called blocking phenomenon.
The other drawback of the conventional image transfer sheet is that the image transfer sheet tends to curl during the storage, so that there easily occurs the problem of paper jam in the copying machine.
When a large amount of silicone oil is added to the undercoat layer of the image transfer sheet in order to eliminate the above-mentioned blocking phenomenon, a transporting roller in the copying machine cannot work normally due to slippage, which consequently induces the paper jam in the copying machine. There is an increasing demand for both the prevention of blocking phenomenon of the image transfer sheets during storage and the improvement of transporting performance of the image transfer sheets in the copying machine.
In the field of thermal image transfer recording, which is different from the technical field of the present invention, there is proposed in Japanese Laid-Open Patent Application 8-25788 a thermal image transfer ink ribbon comprising a release layer (corresponding to a backing layer of the image transfer sheet in the present invention) for eliminating the risk of blocking tendency of the image transfer ribbon. According to this application, a silicone material such as a copolymer or blend of silicone resin; and polyolefin, wax, alkyd resin, long-chain alkyl group containing resin, fluoroplastics and shellac are usable as the materials for use in the release layer. However, in this application, the release layer is provided in order to inhibit the blocking phenomenon, not in light of the prevention of curling and the improvement of transporting performance of the thermal image transfer ribbon in the image forming apparatus.
The conventional image transfer sheet has a further drawback that the adhesion of the undercoat layer thereof to various kinds of image-receiving members is insufficient. For instance, when an image formed on the image transfer sheet is transferred to a T-shirt made of cotton, the transferred image will peel off after repeated washing. In addition, when an image-transferred cloth is ironed after washing, the image on the cloth will soften and fuse again, so that the image will deform and stick to the surface of the iron. Namely, the fixing properties of the transferred image are still insufficient.